A damper device is generally arranged at, for example a power transmission path between an engine and a clutch, in order to absorb a torque fluctuation generated between the engine and a transmission. The damper device generates a torsional force when the torque fluctuation is generated in order to absorb the torque fluctuation by means of elastic force of coil springs and friction force (hysteresis torque) generated by friction materials. In a case where water such as raindrops enters the transmission, and water and/or mud (dirt) enters the damper device, the friction material and a plate (a plate sliding together with the friction material) may rust at surfaces contacting each other. If the friction material and the plate rust, characteristics thereof are changed, and expected functions may not be obtained. Therefore, the known damper device (torque fluctuation absorber) is structured in such a way that an entire surface of the plate facing the transmission is covered, at the same time, a cover member is provided so as to separate sliding surfaces on which the friction material contacts the sliding surface slide from the outside, as a result, foreign objects and water may not enter the damper device, and a level of change in a limit torque value with the passage of time may be reduced (JP2007-218346A).
However, according to the known damper device, an input shaft of a transmission is inserted into a hole (an inner circumference portion) of a cover member of the damper device, and the cover member is supported by the input shaft by means of a seal member or a bush, so that the cover member prevents the input shaft from being eccentric. Therefore, when the damper device is mounted, the damper device needs to be positioned in a manner where the hole of the cover member of the damper device is fit to the input shaft. If the position of the hole of the cover member is not fit to the input shaft, the position of the cover member needs to be adjusted once the input shaft is removed from the damper device.
A need thus exists for a damper device, which is not susceptible to the drawback mentioned above.